1. Technical Field of the Invention
The present invention relates to cellular telephone networks and, in particular, to the terminating call routing process performed within a cellular telephone network.
2. Description of Related Art
Operation of a cellular telephone network to handle an incoming call dialed to a cellular subscriber mobile station is well known. Responsive to receipt at an originating (or gateway) switching node of the incoming call dialed to a mobile station, a location request (send routing) message is sent to the home location register for the dialed mobile station. The home location register then identifies a switching node currently serving the dialed mobile station. A routing request (provide roaming) message is then sent from the home location register to the serving (or visited) switching node to prepare for delivery of the call. The serving switching node determines to some degree the location of the called mobile station (based perhaps on information resulting from a recent registration or paging attempt), assigns an appropriate routing number (for example, a temporary location directory number or a roaming number) for that location, and responds to the home location register with the routing number. The assigned routing number is then forwarded to the originating switching node where it is used to establish a trunk call connection between the originating switching node and the serving switching node to deliver the incoming call to the dialed mobile station. Delivery of the call to the mobile station is then accomplished by establishing a trunk connection with a base station controller connected to a base station currently serving the mobile station. A radio frequency communications link is then established between the base station and the mobile station.